Steam the cauliflower for 6 minutes in a large covered pot with about 1/2 inch of boiling water in the bottom. Drain and cool to room temperature.
Meanwhile, stir together the mayo, mustard, lime juice, garlic, chipotle puree, and salt. Stir in the cilantro, onion, pepper, and cooked cauliflower. Serve at room temperature or chill in the refrigerator.
*** To make the chipotle puree simply blend a can of chipotles in adobo in a small food processor. This freezes really well. I freeze it in 1/2 tablespoon portions in an ice cube tray so I can take one out when needed.